Orthogonal frequency division multiplexing (OFDM) technology is the most widely used multicarrier modulation technology at present. Filter bank multicarrier (FBMC) technology becomes an alternative technology of the OFDM technology due to the advantages of good out-of-band rejection effect and high spectral efficiency.
The multicarrier modulation technology is susceptible to carrier frequency offset (CFO) and time offset, specifically, the frequency offset and the time offset will make inter-symbol interference exacerbated, and cause the performance of an FBMC system deteriorated. Therefore, a reliable and accurate synchronization signal must be designed when designing the FBMC system.
A common synchronization signal sending method in the FBMC system is a data-aided based synchronization signal sending method, including training sequences based on repeated structures. The training sequences based on the repeated structures refer to that a transmitting terminal continuously sends at least two identical training sequences (namely, synchronization signals), and a receiving terminal processes the received signals by means of the same property of sending symbols between the two training sequences to obtain a frequency offset estimated value, so as to achieve frequency synchronization. The characteristics of the synchronization signal sending method lie in that certain protection symbols are reserved before and after the synchronization signal, and no data symbol is sent on the protection symbols, to avoid the interference of the data symbol on a synchronization symbol.
In a design process of the above-mentioned synchronization signal, the inventor finds that at least the following problems exist in the prior art: the transmitting terminal needs to send at least two identical synchronization signals, and the protection symbols need to be arranged before and after the synchronization signals, resulting in a larger cost of the synchronization signals and low spectral efficiency; moreover, a complicated algorithm is necessary for the receiving terminal to perform the frequency synchronization.